The Collaborative International Dictionary of English v.0.48:

Wilderness \Wil"der*ness\, n. [OE. wildernesse,
   wilderne,probably from AS. wildor a wild beast; cf. D.
   wildernis wilderness. See Wilder, v. t.]
   [1913 Webster]
   1. A tract of land, or a region, uncultivated and uninhabited
      by human beings, whether a forest or a wide, barren plain;
      a wild; a waste; a desert; a pathless waste of any kind.
      [1913 Webster]

            The wat'ry wilderness yields no supply. --Waller.
      [1913 Webster]

   2. A disorderly or neglected place. --Cowper.
      [1913 Webster]

   3. Quality or state of being wild; wildness. [Obs.]
      [1913 Webster]

            These paths and bowers doubt not but our joint
            hands.
            Will keep from wilderness with ease.  --Milton.
      [1913 Webster]

WordNet (r) 3.0 (2006):

wilderness
    n 1: (politics) a state of disfavor; "he led the Democratic
         party back from the wilderness"
    2: a wooded region in northeastern Virginia near Spotsylvania
       where bloody but inconclusive battles were fought in the
       American Civil War
    3: a wild and uninhabited area left in its natural condition;
       "it was a wilderness preserved for the hawks and
       mountaineers" [syn: wilderness, wild]
    4: a bewildering profusion; "the duties of citizenship are lost
       sight of in the wilderness of interests of individuals and
       groups"; "a wilderness of masts in the harbor"

Moby Thesaurus II by Grady Ward, 1.0:

85 Moby Thesaurus words for "wilderness":
   Arabia Deserta, Chinese puzzle, Death Valley, Gordian knot,
   Lebensraum, Rube Goldberg contraption, Sahara, air space,
   back country, back of beyond, backcountry, backlands, backwoods,
   barren, barren land, barrens, boondock, boondocks, borderland,
   brush, bush, bush country, bushveld, can of worms, clear space,
   clearance, clearing, complex, desert, desolation, distant prospect,
   dust bowl, empty view, forests, frontier, glade, heath, hinterland,
   howling wilderness, jungle, karroo, knot, labyrinth, living space,
   lunar landscape, lunar waste, maze, meander, mesh, mess,
   open country, open space, outback, outpost, perplex, plain,
   prairie, ravel, salt flat, snafu, snake pit, snarl, steppe, tangle,
   tangled skein, terrain, territory, the bush, timbers,
   uninhabited region, up-country, virgin land, virgin territory,
   waste, wasteland, weary waste, webwork, wheels within wheels,
   wide-open spaces, wild, wild West, wildness, wilds, woodlands,
   woods



Easton's 1897 Bible Dictionary:

Wilderness
   (1.) Heb. midhbar, denoting not a barren desert but a district
   or region suitable for pasturing sheep and cattle (Ps. 65:12;
   Isa. 42:11; Jer. 23:10; Joel 1:19; 2:22); an uncultivated place.
   This word is used of the wilderness of Beersheba (Gen. 21:14),
   on the southern border of Palestine; the wilderness of the Red
   Sea (Ex. 13:18); of Shur (15:22), a portion of the Sinaitic
   peninsula; of Sin (17:1), Sinai (Lev. 7:38), Moab (Deut. 2:8),
   Judah (Judg. 1:16), Ziph, Maon, En-gedi (1 Sam. 23:14, 24;
   24:1), Jeruel and Tekoa (2 Chr. 20:16, 20), Kadesh (Ps. 29:8).

     "The wilderness of the sea" (Isa. 21:1). Principal Douglas,
   referring to this expression, says: "A mysterious name, which
   must be meant to describe Babylon (see especially ver. 9),
   perhaps because it became the place of discipline to God's
   people, as the wilderness of the Red Sea had been (comp. Ezek.
   20:35). Otherwise it is in contrast with the symbolic title in
   Isa. 22:1. Jerusalem is the "valley of vision," rich in
   spiritual husbandry; whereas Babylon, the rival centre of
   influence, is spiritually barren and as restless as the sea
   (comp. 57:20)." A Short Analysis of the O.T.

     (2.) Jeshimon, a desert waste (Deut. 32:10; Ps. 68:7).

     (3.) 'Arabah, the name given to the valley from the Dead Sea
   to the eastern branch of the Red Sea. In Deut. 1:1; 2:8, it is
   rendered "plain" (R.V., "Arabah").

     (4.) Tziyyah, a "dry place" (Ps. 78:17; 105:41).

     (5.) Tohu, a "desolate" place, a place "waste" or "unoccupied"
   (Deut. 32:10; Job 12:24; comp. Gen. 1:2, "without form"). The
   wilderness region in the Sinaitic peninsula through which for
   forty years the Hebrews wandered is generally styled "the
   wilderness of the wanderings." This entire region is in the form
   of a triangle, having its base toward the north and its apex
   toward the south. Its extent from north to south is about 250
   miles, and at its widest point it is about 150 miles broad.
   Throughout this vast region of some 1,500 square miles there is
   not a single river. The northern part of this triangular
   peninsula is properly the "wilderness of the wanderings"
   (et-Tih). The western portion of it is called the "wilderness of
   Shur" (Ex. 15:22), and the eastern the "wilderness of Paran."

     The "wilderness of Judea" (Matt. 3:1) is a wild, barren
   region, lying between the Dead Sea and the Hebron Mountains. It
   is the "Jeshimon" mentioned in 1 Sam. 23:19.